To evaluate the frequency of acute exacerbations over one year in groups of Cystic Fibrosis patients treated with monthly infusions of (1) serum albumin placebo, (2) low dose (200 mg/kg) MEP IVIG, and (3) high dose (400 mg/kg) MEP IVIG. The safety of monthly MEP IVIG infusions will be determined by comparing the incidence of adverse events among the three study groups.